[release-branch.go1.17] net/http: preserve nil values in Header.Clone

ReverseProxy makes a distinction between nil and zero-length header values.
Avoid losing nil-ness when cloning a request.

Thanks to Christian Mehlmauer for discovering this.

For #53423
For CVE-2022-32148
Fixes #53620

Change-Id: Ice369cdb4712e2d62e25bb881b080847aa4801f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/412857
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit b2cc0fecc2ccd80e6d5d16542cc684f97b3a9c8a)
Reviewed-on: https://go-review.googlesource.com/c/go/+/415221
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

diff --git a/src/net/http/header.go b/src/net/http/header.go
index 4c72dcb2c88d254f3e8b81a483bb6b40079f4b37..ef4ee7ffa812298fd2f86013996bef2f000ae038 100644 (file)
--- a/src/net/http/header.go
+++ b/src/net/http/header.go
@@ -101,6 +101,12 @@ func (h Header) Clone() Header {
        sv := make([]string, nv) // shared backing array for headers' values
        h2 := make(Header, len(h))
        for k, vv := range h {
+               if vv == nil {
+                       // Preserve nil values. ReverseProxy distinguishes
+                       // between nil and zero-length header values.
+                       h2[k] = nil
+                       continue
+               }
                n := copy(sv, vv)
                h2[k] = sv[:n:n]
                sv = sv[n:]

diff --git a/src/net/http/header_test.go b/src/net/http/header_test.go
index 47893629194b6a6dedde343b06c73ac0db976f34..80c003551db8674a6ed7ab2c4e1671367d4e94ef 100644 (file)
--- a/src/net/http/header_test.go
+++ b/src/net/http/header_test.go
@@ -235,6 +235,11 @@ func TestCloneOrMakeHeader(t *testing.T) {
                        in:   Header{"foo": {"bar"}},
                        want: Header{"foo": {"bar"}},
                },
+               {
+                       name: "nil value",
+                       in:   Header{"foo": nil},
+                       want: Header{"foo": nil},
+               },
        }
 
        for _, tt := range tests {